Although areas of potential overlap between the fields of Second Language Acquisition (SLA) and World Englishes (WE) may seem obvious, they developed historically in isolation from each other. SLA had a psycholinguistic emphasis, studying the ways in which individuals progressed towards acquisition of a target language. WE studies initially developed a sociolinguistic focus, describing varieties that arose as second languages in former British colonies. This chapter explores the way in which each field could benefit from the other. The SLA emphasis on routes of development, overgeneralization, universals of SLA, and transfer in the interlanguage has relevance to characterizing sub-varieties of WEs. Conversely, the socio-political dimension of early WE studies and the notion of macro- or group acquisition fills a gap in SLA studies which sometimes failed to acknowledge that the goal of second language learners was to become bilingual in ways that were socially meaningful within their societies.